package com.twmacinta.util;

/**
 * Fast implementation of RSA's MD5 hash generator in Java JDK Beta-2 or higher.
 * <p>
 * Originally written by Santeri Paavolainen, Helsinki Finland 1996.<br>
 * (c) Santeri Paavolainen, Helsinki Finland 1996<br>
 * Many changes Copyright (c) 2002 Timothy W Macinta<br>
 * <p>
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Library General Public License as published by the Free
 * Software Foundation; either version 2.1 of the License, or (at your option)
 * any later version.
 * <p>
 * This library is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU Library General Public License for more
 * details.
 * <p>
 * You should have received a copy of the GNU Library General Public License
 * along with this library; if not, write to the Free Software Foundation, Inc.,
 * 675 Mass Ave, Cambridge, MA 02139, USA.
 * <p>
 * See http://www.twmacinta.com/myjava/fast_md5.php for more information on this
 * file and the related files.
 * <p>
 * This was originally a rather straight re-implementation of the reference
 * implementation given in RFC1321 by RSA. It passes the MD5 test suite as
 * defined in RFC1321.
 * <p>
 * Many optimizations made by Timothy W Macinta. Reduced time to checksum a test
 * file in Java alone to roughly half the time taken compared with
 * java.security.MessageDigest (within an intepretter). Also added an optional
 * native method to reduce the time even further. See
 * http://www.twmacinta.com/myjava/fast_md5.php for further information on the
 * time improvements achieved.
 * <p>
 * Some bug fixes also made by Timothy W Macinta.
 * <p>
 * Please note: I (Timothy Macinta) have put this code in the com.twmacinta.util
 * package only because it came without a package. I was not the the original
 * author of the code, although I did optimize it (substantially) and fix some
 * bugs.
 * <p>
 * This Java class has been derived from the RSA Data Security, Inc. MD5
 * Message-Digest Algorithm and its reference implementation.
 * <p>
 * This class will attempt to use a native method to quickly compute checksums
 * when the appropriate native library is available. On Linux, this library
 * should be named "MD5.so" and on Windows it should be named "MD5.dll". The
 * code will attempt to locate the library in the following locations in the
 * order given:
 * 
 * <ol>
 * <li>The path specified by the system property
 * "com.twmacinta.util.MD5.NATIVE_LIB_FILE" (be sure to include "MD5.so" or
 * "MD5.dll" as appropriate at the end of the path).
 * <li>A platform specific directory beneath the "lib/arch/" directory. On Linux
 * for x86, this is "lib/arch/linux_x86/". On Windows for x86, this is
 * "lib/arch/win32_x86/".
 * <li>Within the "lib/" directory.
 * <li>Within the current directory.
 * </ol>
 * 
 * <p>
 * If the library is not found, the code will fall back to the default (slower)
 * Java code.
 * <p>
 * As a side effect of having the code search for the native library,
 * SecurityExceptions might be thrown on JVMs that have a restrictive
 * SecurityManager. The initialization code attempts to silently discard these
 * exceptions and continue, but many SecurityManagers will attempt to notify the
 * user directly of all SecurityExceptions thrown. Consequently, the code has
 * provisions for skipping the search for the native library. Any of these
 * provisions may be used to skip the search as long as they are performed
 * <i>before</i> the first instance of a com.twmacinta.util.MD5 object is
 * constructed (note that the convenience stream objects will implicitly create
 * an MD5 object).
 * <p>
 * The first option is to set the system property
 * "com.twmacinta.util.MD5.NO_NATIVE_LIB" to "true" or "1". Unfortunately,
 * SecurityManagers may also choose to disallow system property setting, so this
 * won't be of use in all cases.
 * <p>
 * The second option is to call com.twmacinta.util.MD5.initNativeLibrary(false)
 * before any MD5 objects are constructed.
 * 
 * @author Santeri Paavolainen <sjpaavol@cc.helsinki.fi>
 * @author Timothy W Macinta (twm@alum.mit.edu) (optimizations and bug fixes)
 */

public class MD5
{
    /**
     * MD5 state
     */
    MD5State state;

    /**
     * If Final() has been called, finals is set to the current finals state.
     * Any Update() causes this to be set to null.
     */
    MD5State finals;

    /**
     * Padding for Final()
     */
    static byte padding[] = { (byte) 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0 };

    /**
     * Initialize MD5 internal state (object can be reused just by calling
     * Init() after every Final()
     */
    public synchronized void Init()
    {
        state = new MD5State();
        finals = null;
    }

    /**
     * Class constructor
     */
    public MD5()
    {
        this.Init();
    }

    /**
     * Initialize class, and update hash with ob.toString()
     * 
     * @param ob
     *            Object, ob.toString() is used to update hash after
     *            initialization
     */
    public MD5(Object ob)
    {
        this();
        Update(ob.toString());
    }

    private void Decode(byte buffer[], int shift, int[] out)
    {
        /*
         * len += shift; for (int i = 0; shift < len; i++, shift += 4) { out[i]
         * = ((int) (buffer[shift] & 0xff)) | (((int) (buffer[shift + 1] &
         * 0xff)) << 8) | (((int) (buffer[shift + 2] & 0xff)) << 16) | (((int)
         * buffer[shift + 3]) << 24); }
         */

        // unrolled loop (original loop shown above)

        out[0] = ((int) (buffer[shift] & 0xff))
                | (((int) (buffer[shift + 1] & 0xff)) << 8)
                | (((int) (buffer[shift + 2] & 0xff)) << 16)
                | (((int) buffer[shift + 3]) << 24);
        out[1] = ((int) (buffer[shift + 4] & 0xff))
                | (((int) (buffer[shift + 5] & 0xff)) << 8)
                | (((int) (buffer[shift + 6] & 0xff)) << 16)
                | (((int) buffer[shift + 7]) << 24);
        out[2] = ((int) (buffer[shift + 8] & 0xff))
                | (((int) (buffer[shift + 9] & 0xff)) << 8)
                | (((int) (buffer[shift + 10] & 0xff)) << 16)
                | (((int) buffer[shift + 11]) << 24);
        out[3] = ((int) (buffer[shift + 12] & 0xff))
                | (((int) (buffer[shift + 13] & 0xff)) << 8)
                | (((int) (buffer[shift + 14] & 0xff)) << 16)
                | (((int) buffer[shift + 15]) << 24);
        out[4] = ((int) (buffer[shift + 16] & 0xff))
                | (((int) (buffer[shift + 17] & 0xff)) << 8)
                | (((int) (buffer[shift + 18] & 0xff)) << 16)
                | (((int) buffer[shift + 19]) << 24);
        out[5] = ((int) (buffer[shift + 20] & 0xff))
                | (((int) (buffer[shift + 21] & 0xff)) << 8)
                | (((int) (buffer[shift + 22] & 0xff)) << 16)
                | (((int) buffer[shift + 23]) << 24);
        out[6] = ((int) (buffer[shift + 24] & 0xff))
                | (((int) (buffer[shift + 25] & 0xff)) << 8)
                | (((int) (buffer[shift + 26] & 0xff)) << 16)
                | (((int) buffer[shift + 27]) << 24);
        out[7] = ((int) (buffer[shift + 28] & 0xff))
                | (((int) (buffer[shift + 29] & 0xff)) << 8)
                | (((int) (buffer[shift + 30] & 0xff)) << 16)
                | (((int) buffer[shift + 31]) << 24);
        out[8] = ((int) (buffer[shift + 32] & 0xff))
                | (((int) (buffer[shift + 33] & 0xff)) << 8)
                | (((int) (buffer[shift + 34] & 0xff)) << 16)
                | (((int) buffer[shift + 35]) << 24);
        out[9] = ((int) (buffer[shift + 36] & 0xff))
                | (((int) (buffer[shift + 37] & 0xff)) << 8)
                | (((int) (buffer[shift + 38] & 0xff)) << 16)
                | (((int) buffer[shift + 39]) << 24);
        out[10] = ((int) (buffer[shift + 40] & 0xff))
                | (((int) (buffer[shift + 41] & 0xff)) << 8)
                | (((int) (buffer[shift + 42] & 0xff)) << 16)
                | (((int) buffer[shift + 43]) << 24);
        out[11] = ((int) (buffer[shift + 44] & 0xff))
                | (((int) (buffer[shift + 45] & 0xff)) << 8)
                | (((int) (buffer[shift + 46] & 0xff)) << 16)
                | (((int) buffer[shift + 47]) << 24);
        out[12] = ((int) (buffer[shift + 48] & 0xff))
                | (((int) (buffer[shift + 49] & 0xff)) << 8)
                | (((int) (buffer[shift + 50] & 0xff)) << 16)
                | (((int) buffer[shift + 51]) << 24);
        out[13] = ((int) (buffer[shift + 52] & 0xff))
                | (((int) (buffer[shift + 53] & 0xff)) << 8)
                | (((int) (buffer[shift + 54] & 0xff)) << 16)
                | (((int) buffer[shift + 55]) << 24);
        out[14] = ((int) (buffer[shift + 56] & 0xff))
                | (((int) (buffer[shift + 57] & 0xff)) << 8)
                | (((int) (buffer[shift + 58] & 0xff)) << 16)
                | (((int) buffer[shift + 59]) << 24);
        out[15] = ((int) (buffer[shift + 60] & 0xff))
                | (((int) (buffer[shift + 61] & 0xff)) << 8)
                | (((int) (buffer[shift + 62] & 0xff)) << 16)
                | (((int) buffer[shift + 63]) << 24);
    }

    private void Transform(MD5State state, byte buffer[], int shift,
            int[] decode_buf)
    {
        int a = state.state[0], b = state.state[1], c = state.state[2], d = state.state[3], x[] = decode_buf;

        Decode(buffer, shift, decode_buf);

        /* Round 1 */
        a += ((b & c) | (~b & d)) + x[0] + 0xd76aa478; /* 1 */
        a = ((a << 7) | (a >>> 25)) + b;
        d += ((a & b) | (~a & c)) + x[1] + 0xe8c7b756; /* 2 */
        d = ((d << 12) | (d >>> 20)) + a;
        c += ((d & a) | (~d & b)) + x[2] + 0x242070db; /* 3 */
        c = ((c << 17) | (c >>> 15)) + d;
        b += ((c & d) | (~c & a)) + x[3] + 0xc1bdceee; /* 4 */
        b = ((b << 22) | (b >>> 10)) + c;

        a += ((b & c) | (~b & d)) + x[4] + 0xf57c0faf; /* 5 */
        a = ((a << 7) | (a >>> 25)) + b;
        d += ((a & b) | (~a & c)) + x[5] + 0x4787c62a; /* 6 */
        d = ((d << 12) | (d >>> 20)) + a;
        c += ((d & a) | (~d & b)) + x[6] + 0xa8304613; /* 7 */
        c = ((c << 17) | (c >>> 15)) + d;
        b += ((c & d) | (~c & a)) + x[7] + 0xfd469501; /* 8 */
        b = ((b << 22) | (b >>> 10)) + c;

        a += ((b & c) | (~b & d)) + x[8] + 0x698098d8; /* 9 */
        a = ((a << 7) | (a >>> 25)) + b;
        d += ((a & b) | (~a & c)) + x[9] + 0x8b44f7af; /* 10 */
        d = ((d << 12) | (d >>> 20)) + a;
        c += ((d & a) | (~d & b)) + x[10] + 0xffff5bb1; /* 11 */
        c = ((c << 17) | (c >>> 15)) + d;
        b += ((c & d) | (~c & a)) + x[11] + 0x895cd7be; /* 12 */
        b = ((b << 22) | (b >>> 10)) + c;

        a += ((b & c) | (~b & d)) + x[12] + 0x6b901122; /* 13 */
        a = ((a << 7) | (a >>> 25)) + b;
        d += ((a & b) | (~a & c)) + x[13] + 0xfd987193; /* 14 */
        d = ((d << 12) | (d >>> 20)) + a;
        c += ((d & a) | (~d & b)) + x[14] + 0xa679438e; /* 15 */
        c = ((c << 17) | (c >>> 15)) + d;
        b += ((c & d) | (~c & a)) + x[15] + 0x49b40821; /* 16 */
        b = ((b << 22) | (b >>> 10)) + c;

        /* Round 2 */
        a += ((b & d) | (c & ~d)) + x[1] + 0xf61e2562; /* 17 */
        a = ((a << 5) | (a >>> 27)) + b;
        d += ((a & c) | (b & ~c)) + x[6] + 0xc040b340; /* 18 */
        d = ((d << 9) | (d >>> 23)) + a;
        c += ((d & b) | (a & ~b)) + x[11] + 0x265e5a51; /* 19 */
        c = ((c << 14) | (c >>> 18)) + d;
        b += ((c & a) | (d & ~a)) + x[0] + 0xe9b6c7aa; /* 20 */
        b = ((b << 20) | (b >>> 12)) + c;

        a += ((b & d) | (c & ~d)) + x[5] + 0xd62f105d; /* 21 */
        a = ((a << 5) | (a >>> 27)) + b;
        d += ((a & c) | (b & ~c)) + x[10] + 0x02441453; /* 22 */
        d = ((d << 9) | (d >>> 23)) + a;
        c += ((d & b) | (a & ~b)) + x[15] + 0xd8a1e681; /* 23 */
        c = ((c << 14) | (c >>> 18)) + d;
        b += ((c & a) | (d & ~a)) + x[4] + 0xe7d3fbc8; /* 24 */
        b = ((b << 20) | (b >>> 12)) + c;

        a += ((b & d) | (c & ~d)) + x[9] + 0x21e1cde6; /* 25 */
        a = ((a << 5) | (a >>> 27)) + b;
        d += ((a & c) | (b & ~c)) + x[14] + 0xc33707d6; /* 26 */
        d = ((d << 9) | (d >>> 23)) + a;
        c += ((d & b) | (a & ~b)) + x[3] + 0xf4d50d87; /* 27 */
        c = ((c << 14) | (c >>> 18)) + d;
        b += ((c & a) | (d & ~a)) + x[8] + 0x445a14ed; /* 28 */
        b = ((b << 20) | (b >>> 12)) + c;

        a += ((b & d) | (c & ~d)) + x[13] + 0xa9e3e905; /* 29 */
        a = ((a << 5) | (a >>> 27)) + b;
        d += ((a & c) | (b & ~c)) + x[2] + 0xfcefa3f8; /* 30 */
        d = ((d << 9) | (d >>> 23)) + a;
        c += ((d & b) | (a & ~b)) + x[7] + 0x676f02d9; /* 31 */
        c = ((c << 14) | (c >>> 18)) + d;
        b += ((c & a) | (d & ~a)) + x[12] + 0x8d2a4c8a; /* 32 */
        b = ((b << 20) | (b >>> 12)) + c;

        /* Round 3 */
        a += (b ^ c ^ d) + x[5] + 0xfffa3942; /* 33 */
        a = ((a << 4) | (a >>> 28)) + b;
        d += (a ^ b ^ c) + x[8] + 0x8771f681; /* 34 */
        d = ((d << 11) | (d >>> 21)) + a;
        c += (d ^ a ^ b) + x[11] + 0x6d9d6122; /* 35 */
        c = ((c << 16) | (c >>> 16)) + d;
        b += (c ^ d ^ a) + x[14] + 0xfde5380c; /* 36 */
        b = ((b << 23) | (b >>> 9)) + c;

        a += (b ^ c ^ d) + x[1] + 0xa4beea44; /* 37 */
        a = ((a << 4) | (a >>> 28)) + b;
        d += (a ^ b ^ c) + x[4] + 0x4bdecfa9; /* 38 */
        d = ((d << 11) | (d >>> 21)) + a;
        c += (d ^ a ^ b) + x[7] + 0xf6bb4b60; /* 39 */
        c = ((c << 16) | (c >>> 16)) + d;
        b += (c ^ d ^ a) + x[10] + 0xbebfbc70; /* 40 */
        b = ((b << 23) | (b >>> 9)) + c;

        a += (b ^ c ^ d) + x[13] + 0x289b7ec6; /* 41 */
        a = ((a << 4) | (a >>> 28)) + b;
        d += (a ^ b ^ c) + x[0] + 0xeaa127fa; /* 42 */
        d = ((d << 11) | (d >>> 21)) + a;
        c += (d ^ a ^ b) + x[3] + 0xd4ef3085; /* 43 */
        c = ((c << 16) | (c >>> 16)) + d;
        b += (c ^ d ^ a) + x[6] + 0x04881d05; /* 44 */
        b = ((b << 23) | (b >>> 9)) + c;

        a += (b ^ c ^ d) + x[9] + 0xd9d4d039; /* 33 */
        a = ((a << 4) | (a >>> 28)) + b;
        d += (a ^ b ^ c) + x[12] + 0xe6db99e5; /* 34 */
        d = ((d << 11) | (d >>> 21)) + a;
        c += (d ^ a ^ b) + x[15] + 0x1fa27cf8; /* 35 */
        c = ((c << 16) | (c >>> 16)) + d;
        b += (c ^ d ^ a) + x[2] + 0xc4ac5665; /* 36 */
        b = ((b << 23) | (b >>> 9)) + c;

        /* Round 4 */
        a += (c ^ (b | ~d)) + x[0] + 0xf4292244; /* 49 */
        a = ((a << 6) | (a >>> 26)) + b;
        d += (b ^ (a | ~c)) + x[7] + 0x432aff97; /* 50 */
        d = ((d << 10) | (d >>> 22)) + a;
        c += (a ^ (d | ~b)) + x[14] + 0xab9423a7; /* 51 */
        c = ((c << 15) | (c >>> 17)) + d;
        b += (d ^ (c | ~a)) + x[5] + 0xfc93a039; /* 52 */
        b = ((b << 21) | (b >>> 11)) + c;

        a += (c ^ (b | ~d)) + x[12] + 0x655b59c3; /* 53 */
        a = ((a << 6) | (a >>> 26)) + b;
        d += (b ^ (a | ~c)) + x[3] + 0x8f0ccc92; /* 54 */
        d = ((d << 10) | (d >>> 22)) + a;
        c += (a ^ (d | ~b)) + x[10] + 0xffeff47d; /* 55 */
        c = ((c << 15) | (c >>> 17)) + d;
        b += (d ^ (c | ~a)) + x[1] + 0x85845dd1; /* 56 */
        b = ((b << 21) | (b >>> 11)) + c;

        a += (c ^ (b | ~d)) + x[8] + 0x6fa87e4f; /* 57 */
        a = ((a << 6) | (a >>> 26)) + b;
        d += (b ^ (a | ~c)) + x[15] + 0xfe2ce6e0; /* 58 */
        d = ((d << 10) | (d >>> 22)) + a;
        c += (a ^ (d | ~b)) + x[6] + 0xa3014314; /* 59 */
        c = ((c << 15) | (c >>> 17)) + d;
        b += (d ^ (c | ~a)) + x[13] + 0x4e0811a1; /* 60 */
        b = ((b << 21) | (b >>> 11)) + c;

        a += (c ^ (b | ~d)) + x[4] + 0xf7537e82; /* 61 */
        a = ((a << 6) | (a >>> 26)) + b;
        d += (b ^ (a | ~c)) + x[11] + 0xbd3af235; /* 62 */
        d = ((d << 10) | (d >>> 22)) + a;
        c += (a ^ (d | ~b)) + x[2] + 0x2ad7d2bb; /* 63 */
        c = ((c << 15) | (c >>> 17)) + d;
        b += (d ^ (c | ~a)) + x[9] + 0xeb86d391; /* 64 */
        b = ((b << 21) | (b >>> 11)) + c;

        state.state[0] += a;
        state.state[1] += b;
        state.state[2] += c;
        state.state[3] += d;
    }

    /**
     * Updates hash with the bytebuffer given (using at maximum length bytes
     * from that buffer)
     * 
     * @param state
     *            Which state is updated
     * @param buffer
     *            Array of bytes to be hashed
     * @param offset
     *            Offset to buffer array
     * @param length
     *            Use at maximum `length' bytes (absolute maximum is
     *            buffer.length)
     */
    public void Update(MD5State stat, byte buffer[], int offset, int length)
    {
        int index, partlen, i, start;
        finals = null;

        /* Length can be told to be shorter, but not inter */
        if ((length - offset) > buffer.length)
            length = buffer.length - offset;

        /* compute number of bytes mod 64 */

        index = (int) (stat.count & 0x3f);
        stat.count += length;

        partlen = 64 - index;

        if (length >= partlen)
        {
            // update state (using only Java) to reflect input

            int[] decode_buf = new int[16];
            if (partlen == 64)
            {
                partlen = 0;
            }
            else
            {
                for (i = 0; i < partlen; i++)
                    stat.buffer[i + index] = buffer[i + offset];
                Transform(stat, stat.buffer, 0, decode_buf);
            }
            for (i = partlen; (i + 63) < length; i += 64)
            {
                Transform(stat, buffer, i + offset, decode_buf);
            }
            index = 0;
        }
        else
            i = 0;

        /* buffer remaining input */
        if (i < length)
        {
            start = i;
            for (; i < length; i++)
            {
                stat.buffer[index + i - start] = buffer[i + offset];
            }
        }
    }

    /*
     * Update()s for other datatypes than byte[] also. Update(byte[], int) is
     * only the main driver.
     */

    /**
     * Plain update, updates this object
     */

    public void Update(byte buffer[], int offset, int length)
    {
        Update(this.state, buffer, offset, length);
    }

    public void Update(byte buffer[], int length)
    {
        Update(this.state, buffer, 0, length);
    }

    /**
     * Updates hash with given array of bytes
     * 
     * @param buffer
     *            Array of bytes to use for updating the hash
     */
    public void Update(byte buffer[])
    {
        Update(buffer, 0, buffer.length);
    }

    /**
     * Updates hash with a single byte
     * 
     * @param b
     *            Single byte to update the hash
     */
    public void Update(byte b)
    {
        byte buffer[] = new byte[1];
        buffer[0] = b;

        Update(buffer, 1);
    }

    /**
     * Update buffer with given string. Note that because the version of the
     * s.getBytes() method without parameters is used to convert the string to a
     * byte array, the results of this method may be different on different
     * platforms. The s.getBytes() method converts the string into a byte array
     * using the current platform's default character set and may therefore have
     * different results on platforms with different default character sets. If
     * a version that works consistently across platforms with different default
     * character sets is desired, use the overloaded version of the Update()
     * method which takes a string and a character encoding.
     * 
     * @param s
     *            String to be update to hash (is used as s.getBytes())
     */
    public void Update(String s)
    {
        byte chars[] = s.getBytes();
        Update(chars, chars.length);
    }

    /**
     * Update buffer with given string using the given encoding. If the given
     * encoding is null, the encoding "ISO8859_1" is used.
     * 
     * @param s
     *            String to be update to hash (is used as
     *            s.getBytes(charset_name))
     * @param charset_name
     *            The character set to use to convert s to a byte array, or null
     *            if the "ISO8859_1" character set is desired.
     * @exception java.io.UnsupportedEncodingException
     *                If the named charset is not supported.
     */
    public void Update(String s, String charset_name)
            throws java.io.UnsupportedEncodingException
    {
        if (charset_name == null)
            charset_name = "ISO8859_1";
        byte chars[] = s.getBytes(charset_name);
        Update(chars, chars.length);
    }

    /**
     * Update buffer with a single integer (only & 0xff part is used, as a byte)
     * 
     * @param i
     *            Integer value, which is then converted to byte as i & 0xff
     */

    public void Update(int i)
    {
        Update((byte) (i & 0xff));
    }

    private byte[] Encode(int input[], int len)
    {
        int i, j;
        byte out[];

        out = new byte[len];

        for (i = j = 0; j < len; i++, j += 4)
        {
            out[j] = (byte) (input[i] & 0xff);
            out[j + 1] = (byte) ((input[i] >>> 8) & 0xff);
            out[j + 2] = (byte) ((input[i] >>> 16) & 0xff);
            out[j + 3] = (byte) ((input[i] >>> 24) & 0xff);
        }

        return out;
    }

    /**
     * Returns array of bytes (16 bytes) representing hash as of the current
     * state of this object. Note: getting a hash does not invalidate the hash
     * object, it only creates a copy of the real state which is finalized.
     * 
     * @return Array of 16 bytes, the hash of all updated bytes
     */
    public synchronized byte[] Final()
    {
        byte bits[];
        int index, padlen;
        MD5State fin;

        if (finals == null)
        {
            fin = new MD5State(state);

            int[] count_ints = { (int) (fin.count << 3),
                    (int) (fin.count >> 29) };
            bits = Encode(count_ints, 8);

            index = (int) (fin.count & 0x3f);
            padlen = (index < 56) ? (56 - index) : (120 - index);

            Update(fin, padding, 0, padlen);
            Update(fin, bits, 0, 8);

            /* Update() sets finals to null */
            finals = fin;
        }

        return Encode(finals.state, 16);
    }

    /**
     * Turns array of bytes into string representing each byte as unsigned hex
     * number.
     * 
     * @param hash
     *            Array of bytes to convert to hex-string
     * @return Generated hex string
     */
    public static String asHex(byte hash[])
    {
        StringBuffer buf = new StringBuffer(hash.length * 2);
        int i;

        for (i = 0; i < hash.length; i++)
        {
            if (((int) hash[i] & 0xff) < 0x10)
                buf.append("0");

            buf.append(Long.toString((int) hash[i] & 0xff, 16));
        }

        return buf.toString();
    }

    /**
     * Returns 32-character hex representation of this objects hash
     * 
     * @return String of this object's hash
     */
    public String asHex()
    {
        return asHex(this.Final());
    }
}